The invention relates to an apparatus and a process for solids-fluid separation and to products obtained by such a process.
It is known to separate solids from gases by imparting a rotating movement to a solids-gas mixture which is entered substantially horizontally and tangentially in a vertical cylindrical body (e.g. a cyclone) from which gas is discharged at the top and solids are discharged from the bottom.
However, in order to attain substantially complete removal of small solid particles (e.g. catalyst fines) from gases, as desired in e.g. catalytic cracking processes, a number of cyclones is usually required even when the bulk of the solids has already been removed in a preceding separation stage (e.g. by means of deflection plates or cyclones). As a consequence of the horizontal feed inlet means extending tangentially from each cyclone body, a housing (e.g. a reactor vessel) having substantial dimensions would be needed to accommodate a number of cyclones.
Alternatively, such cyclones could be placed outside a reactor vessel, thus requiring complex bracing in order to withstand the prevailing pressure differentials at relatively high operating temperatures (e.g. 400.degree.-600.degree. C. inside the cyclones).
Moreover, in both cases undesired coke and hydrogen formation (i.e. after-cracking) may take place in the various dead spaces at said high temperatures during the substantial residence time in such a large apparatus of e.g. hydrocarbon-containing catalyst particles which are being separated from heavy hydrocarbon vapors.
It is further known to use cylindrical cyclones with axial downward entry for solids-gas separation. In conventional multiple cyclone designs, a solids-containing feed stream enters the cyclone assembly from one side horizontally or under a slight angle (e.g. less than 45 degrees) with a horizontal plane which, in the case that such an assembly arranged inside a reactor vessel, would require additional space as discussed hereinabove for cyclones with tangential feed entry. Moreover, such an arrangement would lead to a pressure difference between the cyclones near the feed inlet side and the downstream cyclones, which would cause unequal distribution of solids-containing fluid over the various cyclones.
It has now been found that the aforementioned disadvantages which are inherent to the various types of cyclones can be overcome by particularly arranging tubular elements and inlet- and outlet means in a housing, resulting in a very compact apparatus for a given solids-fluid separation capacity.